The present invention relates generally to aeration assemblies that are utilized in the gasification of liquids, especially for the aeration of water. In particular, the present invention relates to a dual control lateral air manifold assembly for use in water treatment applications that provide improved efficiency and lower costs.
Activated sludge systems are used to break down organic solids in wastewater by aerobic digestion from microorganisms (biomass). The organisms are then recycled and the remaining products are treated water and waste solids. Carbonaceous Biochemical Oxygen Demand (CBOD) is the amount of carbon-based organic matter in the water that is biodegradable. It is measured as Biochemical Oxygen Demand (BOD). Since this organic matter depletes oxygen in the water, the goal is to remove the organic solids in the water and lower the BOD level. This is also known as BOD removal. The level of BOD is controlled so that the final decanted water can be released into streams or rivers.
The basic equation for treating BOD with the activated sludge process is BOD+O2+Bacteria→CO2+H2O (BOD+Oxygen→Carbon Dioxide+Water).
Since the microorganisms use oxygen to break down the suspended solids (SS), oxygen must be introduced into the mixture of water and solids. This mixture is called Mixed Liquor Suspended Solids (MLSS). The amount of oxygen must be great enough for the biomass to break down the solids in the resident time in the waste tank. In order to maximize the amount of oxygen that is dissolved in the water (DO), the oxygen transfer efficiency (OTE) is examined. The more oxygen, the better the biomass can feed and maintain the proper biomass to solids ratio (F:M). The organisms and solids form into an aggregate called floc.
Biological nutrient remove is also a part of the activated sludge process, since nitrogen and phosphorus are elements which can promote the growth of noxious algae in surface waters that received treated waste water. Another demand of oxygen in an activated sludge process is created by oxidizing ammonia to nitrates (nitrification). Nitrification in aerated/aerobic zones or process phases involves the general formula:
Sequence 1: Bacteria Oxidize Ammonia to Nitride while Consuming Oxygen2NH4+(ammonia)+3O2−(oxygen)→2NO2−(nitrite)+2H2O(water)+4H+(strong acid)
Sequence 2: Bacteria Oxidize Nitrite to Nitrate:2NO2+O2→2NO3 
De-nitrification occurs in a non-aerated/anoxic zone or SBR (Sequencing Bath Reactor) sequence. The nitrate (NO3) from the nitrification zone/sequence is fed back to and mixed with the activated sludge aerobic zone/SBR sequence.
The base equation for de-nitrification is as follows:BOS+NO3(or NO2=4H+→CO2+N2+H2O
Phosphorus (P) removal involves an anaerobic zone/sequence→aerobic zone/sequence.
Various types of water-treatment apparatus have been developed and are used, for example, in clarification plants/waste water-processing aerobic digestion tanks. In a typical system, a plurality of aeration elements are disposed on a distribution conduit, whereby the distribution conduit on the one hand serves for the supply of air or gas to the aeration elements, and on the other hand also serves for the securement of the aeration elements. A plurality of distribution conduits can in turn be combined to form a system.
U.S. Pat. No. 5,015,421 to Messner describes a diffusion device that uses a flexible membrane on a rigid, plate-like aeration support element. Due to the structure of the rigid plate that serves as a substrate for the flexible membrane, when the aerating gas bubbles are released through openings provided in the membrane, or when the flow of aerating gas is stopped, the membrane can crease or wrinkle at specific points along the supporting plate, thus causing fatigue and wear at these points and reduced longevity of the aeration element.
An elongated aeration element is disclosed in DE 33 19 161A1. In addition, DE 36 00 234 discloses an apparatus for the aeration of water, according to which individual aeration elements are connected with the distribution conduit via fittings that during assembly are pressed into a bore in the distribution conduit accompanied by elastic deformation, thereby forming a positive connection. However, the aeration elements are plate-shaped elements. Such a connection is not suitable for elongated aeration elements, which can have an aeration length of up to and greater than one meter. When the apparatus moves or if there are flows in the liquid that is to be aerated, the long aeration elements act like lever arms, so that the forces that occur at the connection locations are much greater than is the case with plate-shaped aeration elements.
U.S. Pat. No. 7,497,421 (U.S. '421) by the same inventor describes an apparatus for gasification of liquids, the disclosure of which is incorporated herein by reference. U.S. '421 describes a device in which compressed gas is introduced into a tubular aeration element made up of rigid support tube with a lengthwise, rounded groove and a flexible membrane disposed around the tube. The gas escapes via slits in the membrane. A specialized fitting is provided for attaching the aeration element to a distribution conduit. The tubular aeration element, however, is limited in its aerating efficiency, due to the limited cross sectional area provided for releasing the aerating gas and bubbles into the surrounding volume of liquid.
None of the above art provides an elongated, flattened aeration element with an oval cross section and increased surface area efficiency, which is specifically designed to allow a flexible, inflatable membrane placed around a support member to expand and collapse during operation without fatigue, wear, and a shortened longevity of the aeration element components.
Further, none of the above cited art provides a means for preventing sludge or other particles from entering the interior of the aeration element during use, which can impair or completely inhibit functioning. This can occur if there is a breach of the membrane by an external impact of a sharp object or debris in the surrounding liquid. A backflow of particles or sludge is inhibited by the fine slits of the perforated membrane, acting as check valves in a deflated state of the membrane.